Some vehicles include a diesel internal combustion engine for propulsion. During operation, the diesel internal combustion engine ignites an air/fuel mixture to rotate a crankshaft. Accordingly, the diesel internal combustion engine receives intake air from an intake manifold. Because the intake air is an important part of the combustion process in a diesel internal combustion engine, it is useful to examine the diesel engine airflow. As used herein, the term “diesel engine airflow” means the flow of gases (e.g. air) entering a combustion chamber of a diesel internal combustion engine. The diesel engine airflow may be examined, for example, as a part of a diagnosis procedure. Examining the diesel engine airflow may also be useful to control exhaust gas recirculation (EGR) flow. It is therefore useful to determine the diesel engine airflow irrespective of the intake valve closure strategy employed by the diesel internal combustion engine.